1. Field of the Invention
This invention relates to an ozone removal system for removing ozone produced during operation of devices such as electrostatographic copiers and other types of reproducing machines, laser printers, and facsimile machine.
Devices which utilize electrostatographic processes, such as reproducing machines, laser printers, and facsimile machines, rely on corona discharge devices which emit corona ions. In such devices, corona ions are used for a number of purposes, such as charging photosensitive components uniformly in preparation for receiving images, transferring toner images from the photosensitive components to paper, and discharging photosensitive members in order to assist toner removal. In electrostatographic machines, the photosensitive members are most frequently configured as belts or drums.
In some electrostatographic copying machines, there may be as many as four corona discharge devices. For example, there may be one at a primary charge station for placing an initial charge on a film belt, and others at additional stations for paper charging, detack, and erasing charge from the film. As is well known, each corona discharge device produces ions which interact with oxygen in the air to form ozone. As is also well known, ozone presents a serious health hazard to people, especially people with ailments such as asthma. In addition, it exacerbates allergies, and can cause respiratory discomfort to even the healthiest of individuals. In view of these health hazards, there are now OSHA regulations requiring minimization of ozone emission. Moreover, ozone can deteriorate machinery and can be especially destructive to photosensitive elements such as the film belts employed in many electrostatographic copiers.
The prior art has addressed this problem in a number of ways. A typical ozone-removing device includes either activated carbon or a metal oxide as ozone adsorption agents. Generally, these devices are passive and are placed in the vicinity of ozone-producing components to remove any ozone which happens to drift into contact with the devices. In another approach, the ozone-absorbing device is placed in proximity to a ventilation exit; however, with this approach, ozone can accumulate in dead air locations since ozone is only removed if entrained in an air ventilation stream. With each of these approaches, the ozone-removing devices are relatively large, adding significantly to the size of the overall device.
For many reasons, it is advantageous to both minimize the overall size of office machines and to minimize the size of office machine components. When designing an office machine, the designer functions within size constraints, so the reduction in size of one component may allow the designer to add an additional feature or increase the size of another component. Moreover, if one can reduce the size of a component, the component can perhaps occupy a previously unused void or space within the machine.
While positioning an ozone-absorbing device at a ventilation exit may not consume as much space as positioning ozone-removing devices at every ozone-generating station, positioning at ventilation exits tends to increase the pressure drop and interfere with adequate ventilation of the machine. This can cause undesirable increases in temperature which can adversely affect the operation of the machine and reduce life of its components.
These problems are considered in the patent literature in U.S. Pat. No. 4,853,735 to Kodama et al. In Kodama et al., an ozone-transporting fan is provided for pushing a stream of air over an ozone-producing station to an ozone collection device positioned in front of a ventilating fan used for the entire machine. With the Kodama et al. device, the solution to the ozone problem affects other components of the machine in that the ozone-entraining airstream is blown over various components and evacuated by the general ventilation fan for the entire machine. In a device such as that of Kodama et al., exposure of various machine components to the ozone-containing stream is not entirely precluded so at least the possibility exists of eventual damage to machine components due to continual low level ozone exposure.
In view of the aforementioned considerations, there is a need for apparatus to minimize the deleterious effects of ozone emissions in devices such as office machines which utilize corona chargers.